1. Field of the Invention
The present invention relates generally to a lighting instrument such as a headlight, an auxiliary headlight or the like for a vehicle. More particularly, the present invention relates to improvement of a device for fitting a headlight with a lamp for a vehicle.
2. Background Art
To facilitate understanding of the present invention, a typical conventional device for fitting a headlight with a lamp for a vehicle (hereinafter referred to simply as a device) will be described below with reference to FIG. 5. The device includes a lamp fitting portion 90 for a headlight 10 through which a lamp 20 is received in the interior of the headlight 10. The lamp 20 includes a bayonet flange 21 having three outer pawls 22 radially projecting therefrom. To receive the outer pawls 22 in the lamp fitting portion 90, three recesses 91a are formed on a flange holding portion 91 of the lamp fitting portion 90. As shown in FIG. 5, the flange holding portion 91 is integrated with the headlight 10. The upper end part of the headlight 10 is covered with a turnable cap 92. To firmly hold the outer pawls 22 in the recesses 91a, three cutouts 92a are formed on the cap 92, and moreover, the cap 92 includes three inner pawl portions 92b corresponding to the outer pawls 22.
When the headlight 10 is fitted with the lamp 20, first, the cutouts 92a on the flange holding portion 92 are located in alignment with the recesses 91a of the flange holding portion 91 so that the outer pawls 22 of the bayonet flange 21 are placed on the recesses 91a of the flange portion 91 through the cutouts 92a from above. The lamp 20 is inserted into the headlight 10 by passing past the circular opening defined by the three cutouts 92a and the three inner pawl portions 92b on the cap 92. Thereafter, the cap 92 is turned in a certain direction, e.g., in the clockwise direction until the outer pawls 22 are located below the inner pawl portion 92b in the overlapped state, resulting in the lamp 20 being firmly fitted in the headlight 10 with the aid of the device.
With the conventional device constructed in the above-described manner, however, various requests have been made by users for improving the present properties of the device. Typically, one of the requests is that the lamp 20 be located at the position where it is inserted into in the headlight 10 when the cap 92 is turned in a certain direction, e.g., in the counterclockwise direction, and subsequently, it is immovably held at the position where it is firmly fitted in the headlight 10 when the cap 92 is turned in the clockwise direction. Another request is that there does not arise a malfunction, wherein the cap 92 is readily disconnected from the flange portion 91 during running of a vehicle. Because of these requests, the conventional device becomes unavoidably complicated in structure, resulting in the device being fabricated at an increased cost.